IL-3R subunit expression on AML cells as detected by QRT-PCR. RNA was extracted from AML cells sorted into the subpopulations indicated as described in “Patients, materials, and methods.” Values shown are the levels of expression of β_c (A) and α (B) subunits of the IL-3R relative to the expression of GAPDH arbitrarily set at 1000 for each of 19 patient samples. Each data point represents the value for an individual patient sample. The horizontal bars and adjacent numbers indicate the mean level of expression for each of the α and β_c subunits in the different subpopulations.